1. Field of the Invention
The present invention relates to a toner storage container such as a developing device and an intermediate hopper which are provided to an electrophotographic image forming apparatus such as a copier, a printer, a facsimile, and a multifunction peripheral having functions of those devices. In particular, the present invention relates to a toner-remaining-amount detection sensor for detecting a toner remaining amount in the toner storage container.
2. Description of Related Art
Conventionally, the electrophotographic image forming apparatus such as a copier and a laser printer is provided with a toner replenishing device such as a toner container for replenishing toner from a toner replenishing port to a developing portion (developing device) of the image forming apparatus. In order to stably replenish toner from the toner replenishing device to the developing device, it is important to accurately detect the toner remaining amount in the toner replenishing device. Examples of sensors used for detection of the toner remaining amount include a piezoelectric sensor, a magnetic permeability sensor, and an optical sensor.
The piezoelectric sensor is designed to take out a detection result of application of pressure to a detection surface as an electric signal, and has features of small size, lightweight, and high sensitivity. Further, in order to maintain detection accuracy, a sensor surface is required to be sufficiently cleaned. For example, as disclosed in the first and second related arts, there has been known a technology of cleaning the sensor surface of the piezoelectric sensor through use of a cleaning member.
The magnetic permeability sensor is designed to detect magnetic permeability of developer and output a voltage value corresponding to the detection result. Regarding use for detection of the toner remaining amount in the toner replenishing device, the magnetic permeability sensor is capable of detecting a magnetic one-component toner. However, the magnetic permeability sensor is incapable of detecting a non-magnetic one-component toner or a non-magnetic toner added to a two-component developer.
The optical sensor includes a reflection optical sensor and a transmission optical sensor. For example, as disclosed in the third related art, there has been known a color image forming apparatus capable of detecting a toner remaining amount of each color through use of one toner-remaining-amount detection sensor by converting light from a light emitting portion of the reflection optical sensor into different light for each of a plurality of developing devices and imparting the light to a light receiving portion. Further, as disclosed in the fourth related art, there has been known a method of enhancing detection accuracy by provision of a cleaning member for preventing adhesion of toner to a detection window of the transmission optical sensor.
Still further, as disclosed in the fifth related art, there has been known a collected-toner-amount detection sensor including a detecting filler rotated in accordance with collection of toner, a detection sensor (photo interrupter) in which a light path is blocked or unblocked in accordance with rotation of the detecting filler, and a rubber sheet for preventing toner leakage into an operating space of the detecting filler.
However, the piezoelectric sensor is expensive, and provision of the cleaning mechanism for the sensor surface as in the first and second related arts causes structural complication of the toner replenishing device, which leads to an increase in cost.
Further, in the reflection optical sensor as disclosed in the third and fourth related arts, an inclination of a reflection plate with respect to a light source (light emitting portion) is important, and hence a light emitting direction and an attachment position of the reflection plate are required to have high accuracy. Also in the transmission optical sensor, when a light-emitting-side sensor and a light-receiving-side sensor are separately provided, positional relation of the sensors is important. Accordingly, there are risks that assembly operation becomes more troublesome and complicated and operability is deteriorated, and that sensor sensitivities vary from each other owing to tolerances of components. In addition, as disclosed in the fourth related art, provision of the cleaning mechanism for the detection window leads to deterioration of assembly operability and an increase in cost due to an increase in the number of components.
Meanwhile, in the structure of the fifth related art, the toner remaining amount is detected with toner pressure, and hence it is unnecessary to perform cleaning of the detection surface. However, the rubber sheet and the detecting filler are arranged on a cleaning case (toner collecting container) side, and the detection sensor is arranged on an apparatus main body side. Thus, some attachment states of the cleaning case cause a change of positional relation between the detecting filler and the detection sensor, which leads to a risk that the sensor sensitivities vary from each other. Further, also when the structure of the fifth related art is applied to a toner storage container undetachable from the apparatus main body, attachment positions of the detecting filler and the detection sensor are required to have high accuracy. Thus, there are problems in that assembly operation becomes more troublesome and complicated, and operability is deteriorated.
Further, the rubber sheet described in the fifth related art is triangular in cross-section and asymmetrical. Thus, a deformation degree of the rubber sheet varies depending on directions in which toner pressure is applied, which may lead to a risk of deterioration of sensor sensitivity. High detection accuracy is not required for the purpose of detecting a full state of the cleaning case (toner collecting container). Meanwhile, the toner remaining amount in the developing device and the toner remaining amount in the intermediate hopper for replenishing toner have influence on image quality, and hence it is necessary to detect those toner remaining amounts with high accuracy. In addition, when an easily-deformable thin-film-like rubber sheet is used for higher detection accuracy, there is a risk that the detecting filler presses and breaks the rubber sheet.
Note that, regarding those cases, although description is made by way of an example of detection of the toner remaining amount of the toner replenishing device for replenishing toner to the developing device, there are similar problems in detection of a remaining amount of toner or developer in the developing device.